The present invention relates to a power transmission control device, a power transmitting device, a power receiving device, a non-contact power transmission system, an electronic instrument, a secondary coil position detection method, a primary coil positioning method, and the like.
In recent years, non-contact power transmission (contactless power transmission) that utilizes electromagnetic induction to enable power transmission without metal-to-metal contact has attracted attention. As application examples of non-contact power transmission, charging a portable telephone, charging a household appliance (e.g., cordless telephone handset or watch), and the like have been proposed.
JP-A-2006-60909 discloses a non-contact power transmission device using a primary coil and a secondary coil, for example.
JP-A-2005-6460 discloses technology that detects misalignment of a primary coil and a secondary coil in a non-contact power transmission system. According to the technology disclosed in JP-A-2005-6460, whether or not the relative positional relationship between the primary coil and the secondary coil is correct is detected based on an output voltage of a rectifier circuit of a power receiving device. When the relative positional relationship between the primary coil and the secondary coil is correct, a light-emitting diode (LED) is turned ON to notify the user that the relative positional relationship between the primary coil and the secondary coil is correct. When the relative positional relationship between the primary coil and the secondary coil is incorrect, the LED is not turned ON. In this case, the user manually adjusts the positional relationship between the primary coil and the secondary coil.
In order to accurately position the primary coil and the secondary coil in a non-contact power transmission system, it is desirable to use a dedicated power transmitting instrument (i.e., a primary-side electronic instrument including a power transmitting device) for a secondary-side instrument including a power receiving device, for example. In this case, since it is necessary to provide a dedicated power transmitting stand corresponding to each secondary-side instrument, the versatility of the power transmitting instrument cannot be ensured.
For example, when charging a battery of a portable terminal utilizing a non-contact power transmission system, the external shape (design) of the portable terminal and the secondary coil installation position generally differ depending on the manufacturer even if the size of the portable terminal is identical. Therefore, it is difficult to deal with a plurality of portable terminals produced by different manufacturers using one power transmitting instrument (charger).
Moreover, different types of terminals (e.g., portable telephone terminal and PDA terminal) differ in size, shape (design), and secondary coil installation position. Therefore, it is difficult to deal with different types of terminals using one power transmitting instrument.
If a portable terminal can be charged merely by placing the portable terminal in a given area of a structure (e.g., desk) having a flat surface without using a dedicated power transmitting instrument, the convenience of a non-contact power transmission system can be significantly improved. However, the accurate position of a secondary coil of a portable terminal placed at an approximate position in a given area cannot be determined for the above-described reasons. Therefore, such a next-generation non-contact power transmission system cannot be implemented by the current technology.
According to the technology disclosed in JP-A-2005-6460, although the user can be notified whether or not the primary coil and the secondary coil are positioned correctly, the user must manually adjust the positional relationship between the primary coil and the secondary coil when the positional relationship is incorrect.
According to the technology disclosed in JP-A-2005-6460, since occurrence of mispositioning is determined based on the output from the rectifier circuit of the power receiving device, power must be continuously transmitted from the power transmitting device to the power receiving device. Moreover, the power transmitting device cannot voluntarily acquire coil misalignment information.